(a) Field of the Invention
The present invention relates to an engine torque control apparatus, and in particular, to an engine torque control apparatus and an engine torque control method that stably control engine torque when, in an engine in which an ISA (Idle Speed Actuator) is installed, a variation of a TPS (Throttle Position Sensor) signal converts from an idle state to a part load state or from the part load state to the idle state.
(b) Description of the Related Art
Generally, an ISA is installed in an engine that is mounted on a vehicle. The ISA operates by a PWM (Pulse Width Modulation) signal from an engine control apparatus and adjusts the amount of air flowing into a combustion chamber so as to maintain a target engine RPM on an idle control condition of the engine.
The engine control apparatus analyzes a TPS signal and when a throttle valve is closed, the engine control apparatus determines the engine to be in an idle state, and when the throttle valve is opened, determines the engine to be in a part load state according to the opening degree of the throttle valve.
In case that a variation in load occurs, the engine control apparatus simultaneously adjusts the air amount of the ISA and the ignition timing so as to maintain the target engine RPM.
The conventional engine torque control operation when the engine mounted on the vehicle is changed from the idle state to the part load state will be described with reference to FIG. 5.
As shown in FIG. 5A, if the variation of the TPS signal converts from an idle period to a part load (P/L) period, a control is performed to cancel a torque restriction amount (TQ restriction amount) set in the idle period, and to reduce the ISA opening, as shown in FIG. 5B. This is because the ignition timing is advanced to compensate torque so as to maintain the maximum torque when a driving condition converts from the idle period to the part load (P/L) period, as shown in FIG. 5C.
That is, as shown in FIG. 6, the torque restriction amount set on the idle condition is rapidly cancelled in the part load period, and the ignition timing is rapidly advanced to the normal ignition timing.
In this case, since a transient period is too short, the engine torque is not accurately controlled through the control of the air amount of the ISA and the ignition timing. Accordingly, the engine torque excessively varies, which results in the drop of the engine RPM.
As shown in FIG. 7, when a driving condition converts from the part load condition to the idle state, the torque restriction amount is rapidly applied when the engine enters the idle state, and the air amount of the ISA is rapidly increased. Then, the ignition timing is immediately delayed by the amount corresponding to the torque restriction amount.
In this case, since the transient period is also too short, the engine torque excessively varies, and overshoot occurs in the engine RPM, which causes a loss of fuel consumption.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.